Why an Ideal Choke Coil Has Zero Real Power

An ideal choke coil is a theoretical, perfect inductor. By definition, it has pure inductance (L) and zero electrical resistance (R = 0).

Real power (or “true power”) is the power actually consumed by a circuit and dissipated as work or heat. In AC circuits, real power is consumed only by resistive elements. The formula for real power is:

P = I²R

Since an ideal choke coil has R = 0, the real power consumed is:

P = I² × 0 = 0 W

This can also be explained using the power factor:

1. The power factor is cos φ = R / Z.
2. For an ideal coil, R = 0, so cos φ = 0 / Z = 0.
3. The general formula for real power is P = V × I × cos φ.
4. Since cos φ = 0, the real power is P = V × I × 0 = 0 W.

An ideal inductor does not consume power. It only stores energy in its magnetic field during one half of the AC cycle and returns this energy to the circuit during the other half. This exchange of energy, which does no real work, is called reactive power.

For an ideal coil, the current lags the voltage by exactly 90°, that is, φ = 90°, and since cos(90°) = 0, no real power is consumed.